Data centers may include several hundred or several thousand servers interconnected by high speed switches and routers. Cloud data centers may provide a variety of services, such as web applications, e-mail services, search engine services, etc., for a plurality of customers. In recent years, data centers have transformed computing, with large scale consolidation of enterprise IT into data center hubs and with the emergence of cloud computing service providers.
Virtual machine (VM) technology allows one or more operating systems, or virtual machines, to run concurrently on one physical host system. The advantages of virtual machine technology have become widely recognized. Among these advantages is the ability to run multiple virtual machines on a single host system.
Live migration allows the transfer of a running virtual machine from one host system to another host system without significant disruption of the operating system running in the virtual machine. The goal for live migration is to avoid significant disruption of the running virtual machine. However, some packet loss is acceptable during live migration.
There are a number of reasons for live migration of a virtual machine. These include an increase in the load on the host system currently hosting the virtual machine, the occurrence of a fault in the host system and the temporary unavailability of the host system for hosting a virtual machine due to planned or unplanned maintenance.
During live migration it is desirable to maintain active connections between the migrating virtual machine and other virtual machines. In a virtualized network where each customer address is mapped to a provider address, the changing of the provider address of the migrating virtual machine will cause packets to be dropped because the other virtual machines still have a stale address mapping. Packet loss for extended periods of time will cause the connections to break due to timeouts.